Variation in the restriction map in the Adh region (alcohol dehydrogenase locus) of chromosome II of Drosophila melanogaster and some related species were examined. Insertion/deletion differences outside the transcriptional unit were common. The distribution within Drosophila melanogaster and among the species suggest that such variants are deterious mutants, although they do not have any obvious effect on Adh function. This initial observation is being repeated with a larger sample. It is also being extended to other loci. Gene activity of the various restriction map types is being measured to find evidence of the effect to the insertion/deletion variants.